Recovery of molybdenite from copper-bearing ores



United States Patent 3,351,193 RECOVERY OF MOLYBDENITE FROM COPPER-BEARING ORES Ricardo Maximo Martinez, Nor-walk, Conn., assignor to American Cyanamid Company, Stamford, Conn., a

corporation of Maine No Drawing. Filed Oct. 12, 1964, Ser. No. 403,335 12 Claims. (Cl. 2093) This invention relates to the beneficiation of sulfide ores for the recovery of mineral values occurring therein. More specifically, it relates to the selective flotation of molybdenite (i.e., molybdenum sulfide or moly) from ores containing other sulfide minerals, particularly copper and iron sulfides.

Molybdenite commonly occurs in copper-bearing ores. When such ores are geneficiated by conventional froth flotation processes using flotation reagents, such as xanthates and dithiophosphates, the molybdenite floats with the copper sulfide and iron sulfide minerals. Since copper is the prime value in such ores, flotation plants are operated to produce optimum copper recovery without particular regard for the moly recovery. Recovery of the moly value of the ores has, therefore, in the main been restricted to processes of separating the moly from molycontaining cleaned copper concentrates obtained by flotation processes employing conventional flotation reagents. These processes, however, are both costly and tedious in that they involve the use of expensive reagents as well as extensive processing which often includes special treating steps, such as roasting or steaming. Essentially, in these processes, the separation of the molybdenite from the copper concentrate is accomplished by either depressing the molybdenite with certain reagents while floating the copper or, conversely, by depressing the copper 'while floating the molybdenite. Processes typical of those in current use are briefly described as follows.

(1) STARCH PROCESS (a) The molybdenite is depressed with soluble starch (dextrine). The copper minerals are then re-floated using ethyl xanthate and an alcohol frother.

(b) Theflotation tailings from (a) are roasted at about 450" F. to drive off reagent coatings and lightly oxidize surfaces of the residual copper sulfides and pyrite.

(c) The roasted product from (b) is retreated by flotation with an alcohol frother to reject readily floated insol.

(d) The flotation tailings from (c) are re-floated using fuel oil and a frother to reactivat molybdenite, Moly concentrate from this latter step is recleaned several times by flotation, with provision for re-roasting cleaner concentrate, if necessary, followed by additional cleaning.

(2) FERROCYANIDE-CYANIDE PROCESS filtered, reground, if necessary, and recleaned in several more stages, using sodium cyanide in the final stages to depress residual copper minerals and pyrite.

(3) FERROCYANIDE-HYPOCHLORITE PROCESS (a) The copper minerals are depressed with sodium hypochlorite and sodium ferrocyanide (yellow prussiate of soda) at a pH of 7.5 to 8.5 and the molybdenite floated using fuel oil and a frother as required.

(b) The rougher concentrate from (a) is recleaned 3,351,193 Patented Nov. 7, 1967 'ice in multiple cleaning stages, using additional staged amounts of hypochlorite and ferrocyanide, together with additional frother and fuel oil as necessary.

(4) CAUSTIC SODA-PHOSPHORUS PENTA- SULFIDE PROCESS (5) HEAT TREATMENT PROCESSES (a) The copper minerals are deactivated by either steaming, with or without pressure, or by low temperature roasting, followed by flotation of molybdenite with fuel oil and a frother, as required. Sodium cyanide or sodium ferrocyanide form ore effective copper and pyrite depression may also be used.

(b) The rougher concentrate from (a) is thickened and reground, if necessary, and then recleaned in several stages, with or without the use of staged additions of ferrocyanide and/ or sodium cyanide.

(c) A low temperature roasting step is sometimes used between recleaning steps.

As is well known, the moly-containing cleaned copper concentrates employed as starting material in the current processes contain from about 60 to no more than of the original moly content of the ore, the remainder of the molybdenite having been lost in the rougher and cleaning operations involved in producing the concentrates. Accordingly, the eventual recovery of moly by these processes, even assuming a recovery from the concentrates, is no greater than 72% of that originally present in the ore. Actually, in practice, where a product' (i.e., concentrate) which meets market specifications is produced the recovery is usually no more than about 50-60% 7 While copper is the prime value of these ores, still the recovery of the moly value as high-grade product is highly desirable from an economic standpoint, The art is, therefore, constantly seeking methods to improve the efliciency and/or lower the cost of moly recovery from the ore without at the same time adversely affecting the copper recovery. The present invention is concerned with such a method.

Accordingly, it is the primary object of this invention to provide a more eflicient and economically advantageous method for recovering the moly value of ores containing copper and iron sulfides. Other objects will be apparent from the following description.

It has now been found, in accordance with the present invention, that moly recoveries amounting to from about 60 to as high as 90% or higher of the molybdenite present in the ore can be obtained bya process which is relatively simple and inexpensive compared to current processes. A characterizing feature of this process is that it commences with the low-grade ore per se ora rougher concentrate thereof, rather than a cleaned copper concentrate as employed in the current processes. Broadly, this new process involves the steps of (1) desliming either (a) the ground crude ore per se in pulped form or (b) a rougher concentrate thereof, to give a split at 5-40 microns, (2) repulping the sands fraction from step (1) to a solids content of from about 10 to about 50%, (3) conditioning the pulp from step (2) with an alkali or alkaline earth metal cyanide and sufficient lime to give a pH of 9 or higher, and (4) floating the molybdenite with a hydrocarbon oil, such as fuel oil, kerosene, light lubricating oil, etc., either with or without a frother, such as alcohol, pine oil, cresylic acid, etc., to produce a relatively highgrade molybdenite concentrate. This concentrate may 4 lb. per ton of crude (black) calcium cyanide (50% active ingredient) and 0.5 lb. per ton of calcium oxide to a pH of 11.5. Then, 0.02 lb. of an alcohol frother (a mixture of 5-9 carbon atom aliphatic alcohols) and 0.04 lb. of No. 2

then be cleaned and recleaned to the desired grade. 5 fuel oil were added and flotation effected. After the molyb- It has been found that when the crude ore or the denite was floated out, the copper was reactivated and rougher concentrate is split as described in step (1), the floated out using conventional copper flotation reagents. sands comprise about two-thirds to three-fourths of the The results are shown in Table I.

' TABLE I Percent Weight Assays, percent Distribution, percent Cumulative, percent Product Total Ind. Cu Fe M081 Cu Fe MoS; Cu Rec.

100.00 11. 31 28.1 1. 211 100. 100.0 100.0 23. 22 10. 00 19. 3 1. 543 25. 19. 9 35. 9 71. 7s 12.25 31. 3 1. 031 74. 5 80.1 64.1 71. 73 100.00 12.25 31. 3 1. 031 100.0 100. 0 100.0 2. 97 4.13 7. 24 17. 2 25. 503 2. 4 2. 3 98.2 8.08 11.25 56. 53 11. s 0. 011 51. 9 2. 6 0.1 6. 54 9.12 32. 39 26. 4 0. 016 24.1 7. 7 0.1 5. 93 3. 2s 13. 4s 37. 2 0. 022 9.1 9. s 0. 1 6. 95 9. e0 6. 03 41.4 0. 033 5. 2 12. s 0. a 2. 86 a. 99 4. 61 41. 2 0.033 1. 5 5. 2 0.1 2.35 3.23 3.27 40.2 0. 028 0.9 4.2 0.1 36. 09 50. 23 1. 13 35. 3 o. 024 4. 9 53.8 1.0

weight of the ore or the rougher concentrate and contain from about 60 to as high as 90% of the molybdenite content of the ore or the rougher concentrate; and, in the cast of the rougher concentrate, the original collectors therein are washed out with the slimes. Also, when the sands are conditioned and floated in accordance with steps (3) and (4), the copper is substantially completely depressed and molybdenite recoveries of 75-80% of that present in the sands from the crude ore and close to 100% of that present in the sands of the rougher concentrate are obtained. When the slimes are treated by conventional flotation and the moly recovered thereby added to the moly obtained from the sands fraction, total recoveries of 90% or higher (based on the original moly content of the ore) are obtainable. At the same time, the process does not adversely affect the copper metallurgy, since the copper can be recovered by conventional treatment of the tailings from the moly flotation. It is seen then that while providing substantial improvement in moly recovery in terms of the original moly content of the crude ore the present process at the same time avoids the necessity of employing final copper concentrates as starting materials and the cost attendant therewith. A further economic advantage is afforded by virtue of the substantial reduction It will be seen from the data in Table I that the process of the invention provides (in a single flotation step) a moly concentrate assaying 25.6% M08 which corresponds to 98.2% of the moly content of the sands split from the starting rougher concentrate. Since the sands contained 64.1% of the moly present in the rougher concentrate, the recovery of moly, based on the total concentrate, was 62.6%. At the same time, the copper recovery effected by conventional means from the tailings of the moly flotation was 90.3%. The process of the invention, therefore, does not adversely affect copper recovery.

Example 2 A South American crude ore was ground to about %-200 mesh and deslimed on a laboratory cyclone. The sands were then repulped with water to about 25% solids and conditioned 5 minutes with 0.25 lb. per ton of crude calcium cyanide (50% active ingredient) and 0.5 lb. per ton of calcium oxide to a pH of 11.7. The moly was then floated with 0.04 lb. per ton of No. 2 fuel oil and 0.02 lb. per ton of pine oil. After the moly was out, the copper minerals were floated using conventional copper reagents. The results are shown in Table II.

TABLE 11 Percent Weight Assays, percent Distribution, percent Cumulative, percent Product Total Ind. Cu Fe MOS: Cu Fe MoS; Cu Ree Crude Ore 100.00 1. 483 0.031 100. 0 100.0 Slirnes 20. 44 1.03 1. 5 0.031 14. 2 19. 9 Sands 79. 66 1. 59 0.031 84. 8 80.1 Sands 1 79. 56 1. 59 0.031 100.0 100. 0 Moly Cone 2.36 1. 56 1. 5 0.821 2. 9 76. 7 Cu Gone. 1. 2.86 32. 62 20. 0 0.033 73.3 3. 6 Cu Gone 2. 1.89 7.57 5.2 0.037 11.2 2.8 Tails 72. 45 0.22 0. 7 0. 006 12.5 16. 9

A copper-moly rougher concentrate from Peru was deslimed in a laboratory cyclone. The sands were repulped with water to about 25% solids and conditione 65 process of From Table II, it is seen that upon application of the the invention directly to the ground crude ore, a concentrate assaying 0.82% MoS accounting for 76.7% of the moly content of the sands split from the ore was obtained. Since the sands contained 80.1% of the moly present in the ore, the recovery of moly based on copper recovery from the moly flotation tailings was 84.5%.

Example 3 A copper-moly rougher concentrate from Utah was (1 with 0.5 reground to %200 mesh and deslimed on a laborathe total ore Was 6l.4%. Here again, it is seen that the tory cyclone. The sands were repulped with water and conditioned at about 25% solids with 4.0 lbs. per ton of calcium oxide to a pH of 12.1 and 4.0 lbs. per ton of crude calcium cyanide (50% active ingredient). Then, 0.25 lb. per ton of fuel oil and 0.10 lb. of a mixed 5-9 carbon atom aliphatic alcohol frother were added and flotation effected. After the molybdenite was floated out, the copper was reactivated and floated using conventional copper flotation reagents. The results are shown in Table ingredient), is usually employed. For clarity, therefore, the amounts of these reagents set forth above and in the following claims have reference to the pure reagents, exclusive of impurities which may be present therein. It will be understood further with respect to these reagents that they may be supplied to the process either as such, or they may be formed in situ by the addition to the ore pulp of hydrogen cyanide and an alkali or alkaline earth metal base, such as caustic soda, potash, lime, etc.

As indicated previously, it is necessary that sufficient TABLE III Percent Weight Assays, percent Distribution, percent Cumulative, percent Product Total Ind. Cu Fe M089 Cu Fe MoSg Cu Rec.

. 12. 16 20. 4 2. 149 100. 100. 0 13. 09 17.1 0. 727 25.1 19. 11.87 21.4 2.582 74.9 80.5 11.87 21. 4 2. 582 100. o 100. 0 9. 94 12. 5 23. 597 9. 0 s. 3 34. 51 27. 7 0. 044 75. 5 33. 5 17. 25 23. 3 0. 094 13. 3 10. 0 T5115 41.45 54.07 0.48 19.9 0.016 2.2 50.2

From Table III, it is seen that application of the 25 lime be used to provide a pH of 9 or higher, preferably 9 process to this particular rougher concentrate produced to 11.5, in the flotation pulp. a molybdenite concentrate that runs 23.6% M08 which The amount of water used in the flotation is usually accounts for 98.8% of the moly contained in the sands, that to provide a pulp density of from about 10 to about which in turn accounts for 92% of the total moly in the 50% and, preferably -30% solids. rougher concentrate. The combination of these two fig- Generally, the amount of hydrocarbon oil required is ures shows an overall recovery of 91.0% of the total moly. from about 0.005 to about 0.5 lb. per ton, with about With respect to the Examples 1-3, it will be appreci- 0.01 to about 0.05 lb. per ton being the usual amount. ated that the recoveries obtained as shown therein will Where a frother, such as alcohol, pine oil, cresylic acid, be further increased when the moly recoverable from the etc., are used, the amounts required are generally from slimes is added thereto. The following example shows about 0.001 to about 0.1 lb. per ton with about 0.01 to the results obtained when both the sands and the slimes about 0.05 usually being used. are treated in accordance with the invention. I Is is recognized that alkali or alkaline earth metal cyanides have been used in the presence of lime as copper Example 4 depressants in the recovery of molybdenite from copper- A rougher copper-moly concentrate (from the same bearing ores. However, this use heretofore has been only ore used in Example 1) was deslimed to a split of 72.8% in cleaning operations (generally at the final cleaning to the sand portion and 27.2% to the slime portion by tage) to upgrade cleaned moly concentrates obtained weight. The sands were reground to 90%200 mesh and using other reagents. Thus, the limited effectiveness of the the two products were treated separately using the proccyanide-lime combination as a copper depressant in ess of this invention. The results thus obtained were rougher cvllcefitfates made its use for this P p mathematically combined for final results which are shown in Table IV.

economically unfeasible. Its high effectiveness when employed on the separated sands in accordance with the in- From Table IV, it can be seen that the process when both sands and slimes are treated produced a 96.3% recovery of the total moly contained on the rougher concentrate. The assay of this concentrate was l0.950% M08 Assuming a 90% recovery of this moly on further cleaning an overall moly recovery of 86.5% with a concentrate meeting market specifications is obtained.

The amount of alkali or alkaline earth metal cyanide reagent suitable for use in conditioning the separated sands in the process of the invention will vary depending upon the minerology of the ore but, in general, will be from about 0.05 to about 2.5 lbs. per ton with the usual amount being about 0.250.5 lb. per ton. For economic reasons, technical grades of the reagents will ordinarily be used. For example, in the case of calcium cyanide, the black cyanide of commerce (containing about active stant process was, therefore, totally unexpected. The uniqueness of the present process, therefore, resides in the advantageous combination of processing steps therein, i.e., the combination of (l) the desliming of either the crude ore per se or a rougher concentrate thereof and (2) the use of the cyanide and lime as the copper depressant in the flotation of the moly from the sands obtained in (1) whereby a relatively high-grade moly concentrate is obtained. The process of the invention, therefore, provides an improved and at the same time more economical recovery of the molybdenite, without detraction from the necessary copper recovery.

While the present invention has been described and illustrated herein in terms of specific examples and embodiments thereof, it is not intended that its scope be limited in any way thereby, but only as defined in the following claims.

I claim:

1. A process for recovering molybdenite from an ore containing a relatively small amount of molybdenite and a. relatively large amount of copper sulfide which comprises the steps of (1) desliming a member selected from the group consisting of (a) the crude ore per se in pulped form and (b) a rougher concentrate of the ore to give a split at between about and about 40 microns, (2) repulping the sands fraction from step (1) to a solids content of from about to about 50%, (3) conditioning the pulp from step (2) with (a) from about 0.05 to about 2.5

lbs. per ton of a cyanide compound selected from the group consisting of alkali metal cyanides and alkaline earth metal cyanides, and (b) sufiicient lime to provide a pH therein of at least9 and (4) subjecting the conditioned pulp from step (3) to froth flotation with a hydrocarbon oil to obtain a relatively high-conceutration of molybdenite in the froth.

2. The process of claim 1 wherein the material subjected to desliming in step (1) is the pulped crude ore.

3. The process of claim 1 wherein the material subjected to desliming in step (1) is a rougher concentrate of the ore.

4. The process of claim 1 wherein the pulp formed in step (2) has a solids content of from about to about 30%.

5. The process of claim 1 wherein the cyanide compound is calcium cyanide.

6. The process of-claim 5 wherein the pH of the conditioned pulp in step (3) is from 9 to 11.5.

7. The process of claim 1 wherein the hydrocarbon oil is fuel oil.

8. The process of claim 7 wherein the amount of fuel oil employed is from about 0.01 to about 0.5 lb. per ton of the conditioned pulp.

9. The process of claim 8 wherein a frothing agent is employed along with the fuel oil.

10. The process of claim 5 wherein the calcium cyanide is formed in situ from hydrogen cyanide and lime.

11. A process for recovering molybdenite from an ore containing a relatively small amount of molybdenite and a relatively large amount of copper sulfide which comprises the steps of (1) desliming the crude ore per se in pulped form to give a'split at between about 5 and about 40 microns, (2) repulping the sands fraction from step (1) to a solids content of from about 10 to about (3) conditioning the pulp from step (2) with (a) from about 0.05 to about 2.5 lbs. per ton of calcium cyanide and (b) sufiicient lime to provide a pH therein of from 9 to about 11.5 and (4) subjecting the conditioned pulp from step (3) to froth flotation with fuel oil to obtain a relatively high-concentration of molybdenite in the froth.

12. A process for recovering molybdenite from an ore containing a relatively small amount of molybdenite and a relatively large amount of copper sulfide which comprises the steps of (1) desliming a rougher concentrate or the ore to give a split at between about 5 and about 40 microns, (2) repulping the sands fraction from step (1) to a solids content of from about 10 to about 50%, (3) conditioning the pulp from step (2) with (a) from about 0.05 to about 2.5 lbs. per ton of calcium cyanide and (b) sufficient lime to provide a pH therein of from 9 to about 11.5 and (4) subjecting the conditioned pulp from step (3) to froth flotation with fuel oil to obtaina relatively high-concentration of molybdenite in the froth.

References Cited UNITED STATES PATENTS 1,454,838 5/ 1923 Borcherdt 209-167 1,939,069 12/1933 Lemmon 209---167 2,019,306 10/1935 Handy 209.-167 2,316,743 4/1943 Marsh 209166 2,620,068 12/1952 Allen 209167 HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,351,193 November 7, 1967 Ricardo Maximo Martinez It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 1 line 17, for "geneficiated" read beneficiated column 2 line 22 for "form ore" read for more columns 3 and 4, TABLE I fifth column, line 12 thereof, for "35 3" read 33.5 column 3 line 28 for "cast" read case Signed and sealed this 26th day of November 1968 (SEAL) Attest:

Edward M. Fletcher, Jr, EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A PROCESS FOR RECOVERING MOLYBDENITE FROM AN ORE CONTAINING A RELATIVELY SMALL AMOUNT OF MOLYBDENITE AND A RELATIVELY LARGE AMOUNT OF COPPER SULFIDE WHICH COMPRISES THE STEPS OF (1) DESLIMING A MEMBER SELECTED FROM THE GROUP CONSISTING OF (A) THE CRUDE ORE PER SE IN PULPED FORM AND (B) A ROUGHER CONCENTRATE OF THE ORE TO GIVE A SPLIT AT BETWEEN ABOUT 5 AND ABOUT 40 MICRONS, (2) REPULPING THE SANDS FRACTION FROM STEP (1) TO A SOLIDS CONTENT OF FROM ABOUT 10 TO ABOUT 50%, (3) CONDITIONING THE PULP FROM STEP (2) WITH (A) FROM ABOUT 0.05 TO ABOUT 2.5 LBS. PER TON OF A CYANIDE COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL CYANIDES AND ALKALINE EARTH METAL CYANIDES, AND (B) SUFFICIENT LIME TO PROVIDE A PH THEREIN OF AT LEAST 9 AND (4) SUBJECTING THE CONDITIONED PULP FROM STEP (3) TO FROTH FLOTATION WITH A HYDROCARBON OIL TO OBTAIN A RELATIVELY HIGH-CONCENTRATION OF MOLYBDENITE IN THE FROTH. 